While most of the prior art in the field of spiral binding apparatus relates to the use of metallic wire spirals, two patents specifically relate to the use of plastic spirals. The patent of Penner (U.S. Pat. No. 2,638,609) describes a machine for binding books with special features for aligning the perforations of a sheaf of papers to be bound and to confine the travel of the plastic spiral binding material. The patent of Pfaffle (U.S. Pat. No. 4,249,278) describes a machine for spiral binding which feeds plastic thread from a bulk spool, softens the thread, winds it on a mandrel to form a spiral, cools it to harden and then feeds the rigid spiral into a perforated sheet group.
U.S. Pat. No. 4,378,822 of Morris describes a spiral binding machine with a drive component. However, the mandrel of Morris '822 is fixed, not laterally adjustable as in the present invention, and the mandrel of Morris '822 has a closed end, which requires pre-feeding of the spiral thereon.